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authorJozef Lawrynowicz <jozef.l@mittosystems.com>2020-11-18 11:51:13 +0000
committerJozef Lawrynowicz <jozef.l@mittosystems.com>2020-11-18 11:51:13 +0000
commit99fabbc9739a87ba3433e66792e93b773896790e (patch)
tree6a52b12cc648532f3b38fd102cec221a207188ba /gas/doc
parent40d9d2fd796a184f04a83ca4442fd78034b5e00b (diff)
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Support SHF_GNU_RETAIN ELF section flag
The SHF_GNU_RETAIN section flag is an extension to the GNU ELF OSABI. It is defined as follows: ========================================================= Section Attribute Flags +-------------------------------------+ | Name | Value | +-------------------------------------+ | SHF_GNU_RETAIN | 0x200000 (1 << 21) | +-------------------------------------+ SHF_GNU_RETAIN The link editor should not garbage collect the section. ========================================================= The .section directive accepts the "R" flag, which indicates SHF_GNU_RETAIN should be applied to the section. There is not a direct mapping of SHF_GNU_RETAIN to the BFD section flag SEC_KEEP. Keeping these flags distinct allows SHF_GNU_RETAIN sections to be explicitly removed by placing them in /DISCARD/. bfd/ChangeLog: * elf-bfd.h (enum elf_gnu_osabi): Add elf_gnu_osabi_retain. (struct elf_obj_tdata): Increase has_gnu_osabi to 4 bits. * elf.c (_bfd_elf_make_section_from_shdr): Set elf_gnu_osabi_retain for SHF_GNU_RETAIN. (_bfd_elf_final_write_processing): Report if SHF_GNU_RETAIN is not supported by the OSABI. Adjust error messages. * elflink.c (elf_link_input_bfd): Copy enabled has_gnu_osabi bits from input BFD to output BFD. (bfd_elf_gc_sections): gc_mark the section if SHF_GNU_RETAIN is set. binutils/ChangeLog: * NEWS: Announce SHF_GNU_RETAIN support. * readelf.c (get_elf_section_flags): Handle SHF_GNU_RETAIN. Recognize SHF_GNU_RETAIN and SHF_GNU_MBIND only for supported OSABIs. * testsuite/binutils-all/readelf.exp: Run new tests. Don't run run_dump_test when there isn't an assembler available. * testsuite/lib/binutils-common.exp (supports_gnu_osabi): Adjust comment. * testsuite/binutils-all/readelf-maskos-1a.d: New test. * testsuite/binutils-all/readelf-maskos-1b.d: New test. * testsuite/binutils-all/readelf-maskos.s: New test. * testsuite/binutils-all/retain1.s: New test. * testsuite/binutils-all/retain1a.d: New test. * testsuite/binutils-all/retain1b.d: New test. gas/ChangeLog: * NEWS: Announce SHF_GNU_RETAIN support. * config/obj-elf.c (obj_elf_change_section): Merge SHF_GNU_RETAIN bit between section declarations. (obj_elf_parse_section_letters): Handle 'R' flag. Handle numeric flag values within the SHF_MASKOS range. (obj_elf_section): Validate SHF_GNU_RETAIN usage. * doc/as.texi: Document 'R' flag to .section directive. * testsuite/gas/elf/elf.exp: Run new tests. * testsuite/gas/elf/section10.d: Unset SHF_GNU_RETAIN bit. * testsuite/gas/elf/section10.s: Likewise. * testsuite/gas/elf/section22.d: New test. * testsuite/gas/elf/section22.s: New test. * testsuite/gas/elf/section23.s: New test. * testsuite/gas/elf/section23a.d: New test. * testsuite/gas/elf/section23b.d: New test. * testsuite/gas/elf/section23b.err: New test. * testsuite/gas/elf/section24.l: New test. * testsuite/gas/elf/section24.s: New test. * testsuite/gas/elf/section24a.d: New test. * testsuite/gas/elf/section24b.d: New test. include/ChangeLog: * elf/common.h (SHF_GNU_RETAIN): Define. ld/ChangeLog: * NEWS: Announce support for SHF_GNU_RETAIN. * ld.texi (garbage collection): Document SHF_GNU_RETAIN. (Output Section Discarding): Likewise. * testsuite/ld-elf/elf.exp: Run new tests. * testsuite/ld-elf/retain1.s: New test. * testsuite/ld-elf/retain1a.d: New test. * testsuite/ld-elf/retain1b.d: New test. * testsuite/ld-elf/retain2.d: New test. * testsuite/ld-elf/retain2.ld: New test. * testsuite/ld-elf/retain2.map: New test. * testsuite/ld-elf/retain3.d: New test. * testsuite/ld-elf/retain3.s: New test. * testsuite/ld-elf/retain4.d: New test. * testsuite/ld-elf/retain4.s: New test. * testsuite/ld-elf/retain5.d: New test. * testsuite/ld-elf/retain5.map: New test. * testsuite/ld-elf/retain5lib.s: New test. * testsuite/ld-elf/retain5main.s: New test. * testsuite/ld-elf/retain6a.d: New test. * testsuite/ld-elf/retain6b.d: New test. * testsuite/ld-elf/retain6lib.s: New test. * testsuite/ld-elf/retain6main.s: New test.
Diffstat (limited to 'gas/doc')
-rw-r--r--gas/doc/as.texi3
1 files changed, 3 insertions, 0 deletions
diff --git a/gas/doc/as.texi b/gas/doc/as.texi
index 278de41..84a7e61 100644
--- a/gas/doc/as.texi
+++ b/gas/doc/as.texi
@@ -6659,6 +6659,9 @@ section is a member of a section group
section is used for thread-local-storage
@item ?
section is a member of the previously-current section's group, if any
+@item R
+retained section (apply SHF_GNU_RETAIN to prevent linker garbage
+collection, GNU ELF extension)
@item @code{<number>}
a numeric value indicating the bits to be set in the ELF section header's flags
field. Note - if one or more of the alphabetic characters described above is